Dynamo-electric machine.



D. HALL.

. DYNAMO ELECTRIC MACHINE. APPLICATION FILED JLN.15, 1996,

982,81 3. Patented Jan. 31, 1911."

3 SHEETS-SHEET'I.

Q L w w v i 1 I I [5w I Q Q i I I Eva/Wan: Min/5555s: David Hall.

I .gf ing D HALL.

DYNAMO ELECTRIC MACHINE.

APPLICATION FILED JAN. 15', 1906. 982,813. Patented Jan. 31,1911.

INVENTDR' flavl'd Jiall g J I I BY Xyg W i DQ'HALL. DYNAMO' ELBGTRIGMACHINE. APPLICATION FILED It]. 15, 1906.

Patented Jan 31,1911.-

Wmvzsses u H w a A w fl g a i a E: M n m I? rm: NORRIS PETERS cm,WAsnlNcrou, uuc.

' rent than do the other brushes.

UNITED STATES PATENT OFFICE.

DAVID HALL, OF NORWOOD, OHIO, ASSIGNOR TO THE BULLOCK ELECTRIC MANUFAC-TURING'COMPANY, A CORPORATION OF OHIO.

DYNAMO-ELECTRIC MACHINE.

Specification of Letters Patent.

Patented Jan. 31, 1911.

Application filed January 15, 1906; Serial No. 296,041.

To all whom it may concern:

Be it known that 1, DAVID HALL, a citizen of the United States, residingat Norwood, in the county of Hamilton and State of Ohio, have inventedcertain new and useful Improvements in D ynamo-Electric i Iachines, ofwhich the following is a full, clear, and exact specification.

My invention relates to improvements in dynamo-electric machines andespecially to machines of the double commutator type having a balancingwinding for neutralizing the armature reaction.

In operating double commutator generators, considerable difficulty hasbeen experienced due to an unbalancing of the load on the machine; thatis, due to an unsymmetrical distribution of the current between thecommutators of the generator armature. This is especially true ofmultipolar machines employing a large number of carbon brushes orcollectors. In such machines there is a tendency for certain of thebrushes on the machine, or all of the brushes on a single commutator, tograb the load, as it is called. This so called grabbing of the loadtakes place as follows :As the result of some local disturbance, suchfor instance as dirt or dust between the commutator and brushes, or abrush of peculiar composition, or due to a relatively low resistancefeeder connection, or for some other reason, the path for the currentfrom the armature winding through certain of the brushes is'at first ofslightly lower resistance than is the path through certain otherbrushes. This condition causes the first mentioned brushes to at firsttake a little more current than is taken by the other brushes. As iswell known, a carbon brush has less-resistance when hot than when cool,and as the resistance of said brush drops very rapidly as the currentdensity and consequently the heat increases, it will be seen that thefirst mentioned brushes offer less and less resistance to the passage ofcur- As a result said first mentioned brushes heat up quite rapidly,andas they heat up, they take more and more of the current until, assometimes happens, the brushes on a single commutator and brush holderson one side of the machine are greatly overloaded, since they aredesigned to carry one-half of the current of the machine and not thewhole current. This unbalanced condition may produce considerablesparking and it may happen that the brushes, brush holders, andconnnutators are entirely destroyed as the result of the sparking andexcessive heating. To prevent this unequal division of current betweenthe two commutators, it has been proposed to increase the resistance ofeach side of the machine by placing in series with the brushes of thecommutators equal ohmic resistances. This method, while it maintains asubstantially equal distribution of current between the commutators,results in considerable loss in energy.

In large machines intended to operate under different conditions ofload, it is customary to employ an auxiliary field .winding, theconductors of which are usually located in slots in the faces of thefield poles. This winding is in series with the armature winding orwindings and is so arranged that the magnetic field produced by thecurrent carried thereby will neutralize or balance the armaturereaction, or the field distorting action of the armature, and istherefore called a balancing winding.

The object of my invention is to so arrange the auxiliary field orbalancing winding or windings on a double commutator machine that it orthey tend to maintain an equal division of current between thecommutators.

A further object is to provide improved bridging members between theends of the pole pieces, having slots for the reception of conductors ofthe balancing winding. By means of these slotted bridging members andthe slots in the faces of the pole pieces the winding can be equallydistributed around the armature.

which are bridged by non-magnetic mem bers, which pole tips and bridgingmembers are slotted to receive two distributed balancing windings, oneof which is connected in series with the brushes of one commutator andthe other of which is connected in series with the brushes of the othercommutator, whereby they will not only balance the armature reaction andreduce sparking at the brushes. but will also serve to maintain an equaldivision of current between the two commutators.

My invention still further consists in the details of construction, andcombinations of elements, described in the specification and set forthin the appended claims.

For a better understanding of my invention, reference is had to theaccompanying drawings forming a. part of this specification, in whichFigure 1 is a sectional elevation 01' a portion of a dynamo-electricmachine embodying my invention; Fig. 2 is an elevation of a portion ofthe field member of the machine showing the slotted pole tips andslotted bridging members between the pole tips; Fig. 3 is a view of thesame looking toward the inner faces of the pole pieces, parts beingremoved for the sake of clearness; Fig. 4: is an elevation of one of thenon-magnetic bridging members; Fig. 5 is a top view of the same; Fig. 6is a bottom view of the same; Fig. 7 is a diagrammatic view showing thetwo balancing windings and their connections; and Fig. 8 is stillanother diagrammatic view showing the arrangement of the balancingwindings.

Referring to the figures of the drawing, 1 have shown at 10 a. shaft ofthe machine to which is attached the armature 11, and conunutators 12and 13 located at each side of the armature. The segments of the twocommutators are connected to the armature winding or windings in theWell known manner. Brushes 141- shown in Figs. 7 and S bear on thecommutators. The field frame 15 which surrounds the armature, hasconnected thereto in any desired manner, a number of radial, inwardlyprojecting, laminated pole pieces 16. There may be any desired number ofpoles, eight being shown in Fig. 7. Each pole piece has a. main fieldcoil 17, which is supported on the seat 17. Mounted on bolts whichextend laterally from the field frame are rollers 18 which support brushrings or yokes 19 in the usual manner.

Each of the laminated pole pieces has a pole tip 20 which extends beyondthe field coils. Each pole tip is provided with a plurality of equallyspaced, partially closed slots 21. These slots are preferably punched inthe sheet metal laminations of the pole piece by dies. Each pole tip hasat each side a projection 22 which has an inwardly inclined portion forsupporting the non-magnetic bridging members 23. Each bridging member,shown in detail in Figs. 4, 5 and 6, is provided with open slots 24, ofthe same width and spaced the same as are the slots 21 in the pole tips.These slots 24 are preferably milled in the bridging member. As shown inFig. 3, between each adjacent pair of pole tips there are three spacedbridging members. The bridging members may, if desired, be cut in anydesired widths from a section which has been provided with the milledslots 2%. Each bridging member is provided with two oppositely extendinglugs or projections 25 having inclined faces 26 which fit snugly on theinclined faces of the projecting portions 22 of the pole tips. Screws 27pass through holes or openings 28 in the lugs or projections and intotapped holes in the hole tips. By this means the bridging members areheld securely in place. As is clearly shown in Fig. 2, the slots in thepole tips and bridging members are closely arranged and the slotted poletips and bridging members completely envelop the armature. The purposeof these slots is to receive the auxiliary distributed field winding orbalancing windings which are commonly employed to neutralize or balancethe armature reaction and prevent the distortion of the field. Aspreviously stated the currents on the two sides of the double commutatormachine may become unequal unless some means is provided for maintainingan equal division of the current.

Reference is now had to Figs. 7 and S. It has been proposed to addbetween the points A and B on each side of the machine orin series withthe brushes on each commutator, a certain predetermined ohmicresistance. The ohmic resistances maintain practically an equal divisionof current between the commutators for the following reason: If thereare no such ohmic resistances, any inequality, however slight and fromwhatever cause, in the division of the current between the twocommutators tends to increase, because the brushes on the more heavilyloaded commutator are heated by the passage of current more than thoseon the more lightly loaded commutator, and. the resistance of carbondecreasing with its temperature, the hotter brush-es take more and moreof the current and continue to rise in temperature until they carrypractically the entire current. Because of this unstable balance ofparts of the current, the commutator and brushes which take the greatershare of the current are greatly overloaded. for they are designed tocarry only one half of the current and not all of it. By insertingohmic. resistances in each branch of the circuit before the two branchesare re-united outside of the armature, the balance between the two partsof the current is rendered more stable, for a decrease in the resistanceof one set of brushes will decrease the total resistance of that branchbut slightly in comparison to the resistance of the whole branch, and bymaking the ohmic resistances of ma.- terial having a positivetemperature co-eliicient of resistance as would commonly be done, eventhis slight decrease may be compensated for by the increased resistanceof such ohmic resistances. Instead of employing for this purpose mereohmic resistances in series with the brushes of each commutator, which,as is understood, causes a useless waste of energy, I employ in thiscase two auxiliary field windings, and so arrange and connect them thatthey will not only balance the armature reaction, but will also serve tomaintain an equal division of current between the brushes of the twocommutators. I employ for this purpose two separate balancing windingswhich are equally distributed about the armature, both windings beingplaced in the same slots. I connect one of these balancing windings inseries with the brushes of one commutator, and the other balancingwinding in series with the brushes of the other commutator. By thisarrangement of the two windings an equal division of current ismaintained without the unnecessary waste of energy incident to the useof ordinary ohmic resistances. Two conductors of the balancing windingslocated in the same slot are shown respectively in Fig.

l at 29 and 30. The balancing windings, however, are shown more clearlyin Figs. '7 and 8 at 31 and 32. In Fig. 7, two different views of thefield frame are shown in full and dotted lines for the sake ofclearness. The full and dotted lines represent respectively the frontand rear ends of the ma chine. The main terminals are shown at 33 and34. The paths of the current through the machine are as follows: Currententers at the negative terminal 33 and at the point A divides and passesequally (if the machine is properly balanced) to the cross connector 35,joining the negative brushes on the commutator 12, and to the crossconnector 36, joining the negative brushes of the commutator 13. Thecurrent then passes through the armature to the positive brushes andequally through the two balancing wind-.

ings 31 and 32, shown clearly in Figs. 7 and 8, and then to the positiveterminal 34;. In Fig. 7 the main field coils 17 are shown in shunt tothe terminals 33 and 34.

The balancing windings may be inserted through the narrow openingsleading to the slots in the pole tips, and will be retained therein bythe overhanging portions of the iron teeth. As is shown in Fig. 4, thebridging members are provided with open slots. It is customary to retainconductors in open slots by wedges which engage grooves in the sides ofthe teeth. Since the milling of the grooves which hold the retainingwedges in place is expensive, I prefer to retain the conductors in theslots of the bridging members by strips or plates 37 of non-magneticmaterial, which strips are preferably secured to the inner faces of theteeth by screws In Fig. the strips have been omitted from three of thebridging members.

I aim in my claims to cover all modifications which do not involve adeparture from the spirit and scope of my invention.

\Vhat- I claim as new and desire to secure by Letters Patent is 1. In adynamo-electric machine, an armature, a plurality of commutators,brushes bearing on said commutators, main field coils, and auxiliaryfield coils for preventing sparking at the brushes, said auxiliary fieldcoils being connected in parallel paths which extend through therespective con1 mutators.

2. In a dynamo-electric machine, an armature, a plurality ofcoimnutators, brushes bearing on said comnmtators, a main field winding,and auxiliary field windings for neutralizing the armature reaction,said lat ter windings being connected in parallel paths which extendthrough the respective commutators.

3. In a double-commutator dynamo-electric machine, balancing coils forneutralizing the armature reaction, one portion of said coils being inseries with the brushes of one commutator and another portion being inseries with the brushes of the other commutator.

1. In a dynamo-electric machine, an armature, two commutators connectedto the armature winding, a field member having main field coils,stationary balancing conductors adjacent to the armautre and parallel tothe conductors thereof, a portion of said stationary conductors being inseries with the brushes on one commutator, and another portion being inseries with the brushes on the other commutator.

5. In a dynamo-electric machine, an ar mature, two commutators therefor,brushes bearing on said commutators, and stationary conductors equallydistributed about the armature and adjacent thereto, one half of saidstationary conductors being in series with the brushes of onecommutator, and the other half being in series with the brushes of theother commutator.

6. In a dynamo-electric machine, an ar mature, two commutator-s, brushesbearing on said commutators, a main field winding, and two auxiliaryfield windings for balancing the armature reaction, one of saidauxiliary windings being in series with the brushes of one commutatorand the other auxiliary winding being in series with the brushes of theother commutator.

7. In a dynamo-electric machine, an armature, a plurality ofeommutators, brushes bearing on said eommutators, main field coils, andauxiliary field coils equally distributed about the armature forbalancing the armature reaction, said latter coils be- 7 ing dividedinto equal groups, each of which is in series with the brushes of one ofsaid commutators.

8. In a dynamo-electricmachine, an armature, two commutators, brushesbearing thereon, a main field winding, and two auxiliary field windingsdistributed in slots about the armature for balancing the armaturereaction, each of said auxiliary windings being in series with thebrushes of one' of said eonnnutators.

9. In a double-commutator dynamo-electric machine, an armature, twocommutators, field poles, bridging members between the ends of the fieldpoles, said field poles and bridging members having equally distributedslots, and two auxiliary field windings for balancing the armaturereaction, said windings being located in said slots and respectivelyconnected in series with the brushes of said commutators.

10. In a dynamo-electric machine, an armature, a plurality ofconnnutators, brushes bearing on said eommutators, a main field winding,and auxiliary field windings connected in parallel paths which includebrushes bearing on the respective commutators.

11. In a dynamo-electric machine, anarniature, a plurality ofcommutators, brushes bearing on said eommutators, main field coils, andauxiliary field coils, said latter coils being divided into equalgroups, each of which is in series with the brushes of one of saidcommutators.

12. In a dynamo-electric machine, an armature, two commutators, brushesbearing thereon, a main field winding, and two auxiliary field windings,each of said auxiliary windings being in series with the brushes of oneof said eommutators.

13. A dynamo-electric machine, comprising an armature provided with aplurality of commutators, brushes for the eommuta tors, and fieldwindings in series respectively with brushes on the difierentco1nmutators, said field windings being arranged in such a manner as tomaintain the proper division of current between such brushes.

14. A dynan1o-electric machine having a single armature winding, twoconnnutators connected to said winding, and a separate field winding inseries with each commutator.

15. In a dynamo-electric machine, an armature, two commutators therefor,a main field winding, and two distributed compensating or balancinwindings, one of said compensating windings being in series with eachcommutator.

In testimony whereof I affix my signature, in the presence of twowitnesses.

DAVID HALL.

Witnesses:

ARTHUR F. ISIWIS, FRED J. KINsEY.

